Re: internal doses monitoring in Nuclear Medicine

[Ccja@aol.com]

This is only a sideways answer, but, bear in mind that we're "starting" with
Mo99 as the parent, with a <3 day halflife. Metastable Tc99 has a physical
halflife of 6h. The "true" daughter, Tc99, has a halflife of 10E5y. (I hope
that exponent is right.) There is no time for ingrowth, so that any amount of
Ru99 could be present in the body, chemotoxic or not. One imagines that the
FDA, and IRB's approving IND Phase I studies, do take account of this issue,
when considering new radionuclides for use in pharmaceuticals.

What I'd like to know is if toxicity studies, of the kind Al's asking about,
and associated pathway analyses, are done for reactor waste. Since the
reactor is continuously producing Mo99, for extended intervals of time, there
is time for ingrowth of Tc99 (in fact, I thought that it, and I129, were
among the longlived products of chief interest). So, millenia down the pike,
there will be Ru99 in the waste. Will it go anywhere, and if so, how fast,
and what would happen to someone who ingested/inhaled it? Maybe someone far
more knowledgeable than I (Gene Carbaugh?) will favor us with an opinion.

Chris Alston
ccja@aol.com